(Windows Internet Naming Service) Name resolution software from Microsoft that runs in Windows NT and 2000 servers. It converts NetBIOS names to IP addresses. Windows machines that are named as a PC in a workgroup rather than in a domain use NetBIOS names, which must be converted to IP addresses if the underlying transport protocol is TCP/IP.

Windows machines identify themselves to the WINS server, so that other Windows machines can query the server to find the IP address. Since the WINS server itself is contacted by IP address, which can be routed across subnets, WINS allows Windows machines on one LAN segment to locate Windows machines on other LAN segments by name.

When a computer is assigned an IP address by DHCP, the WINS database is updated. In a Windows-only network, WINS is queried for name resolution. In a mixed environment, a Unix machine has to query the Microsoft DNS server, which in turn queries the WINS server, because the DHCP in Windows NT does not update the DNS server. The DHCP in Windows 2000 does, however, update the DNS server (Dynamic DNS). The "Internet" in the WINS name refers to the enterprise internet (small "i"), not the public Internet. See DNS.